The introduction of the video display terminal has brought on a substantial change in the office, school and home environment. These new labor saving devices contain, in the most cases, a cathode ray tube as a part of a video display terminal linked to a computer.
Not very many years ago, video display terminals were used on a regular basis only by computer professionals and in limited speciality fields such as air transportation and typesetting. In the recent years the use of such display devices has experienced a rapid growth to the extent that in 1985 there are estimated to be thirteen million video display terminals in use in the United States and Canada alone. The phenomenal growth in the use of such devices has brought a parallel growth in the number of people using such devices. It is estimated that 40-50% of American workers will be making daily use of video display terminals by 1990 at more than thirty-eight million video display terminal stations in factories, schools and offices.
A growing number of children are now using video display terminals in the class room as computers become an integral part of every school program. In addition, the children have extensive use of video display terminals for recreational purposes, such as video games and home computers.
The increased use of video display terminals has several side effects that need consideration. Included in those effects are:
1. X-ray radiation is given off as a secondary emission from the impact of high speed electrons on the viewing screen.
2. Ultraviolet radiation and visible light are given off from the excitation of the phosphors on the inner surface of the screen.
3. Infrared radiation is produced from the heat generated on the viewing screen by the impact of electrons and the excitation of the phosphors.
4. Pulsating very low frequency fields (VLF) at 15-20 Khz are generated by the electrical pulses which cause the beam to go "on" and "off" eleven million times a second.
5. Radio frequencies are also generated by pulsations coming from the coordinating circuits.
6. Extremely low frequencies (ELF) of 30-60 Hz are produced from the electrical pulses which cause the beam to move vertically in order to refresh the full frame 30 to 60 times a second.
7. Static electricity is also produced as a result of electrons being ejected from the electron beam. These electrons build up on the screen and surrounding space.
During recent years, evidence of video display terminal related illnesses has surfaced and an increasing number of health complaints have been reported to the National Institute of Occupational Savety and Health (NIOSH) in the United states. The complaint rate has reached a level where video display terminal operators are number one on OSHA's complaint list. These health complaints have initiated an increase in research into the possible health effects of specifically radiation emissions from the video display terminal. The present stage of this research indicates that the health impact most likely is generated by the high levels of non-ionizing radiation emitted from video display terminals. A number of scientific studies have shown that such radiation is biologically very active and has serious adverse impact on animal embroys, as well as creating a significantly higher cancer rate in animals and humans.
It is also observed that the low level radiation and the extremely low level radiation emitted from video display termnals has a very high electric component and a much lower magnetic component.
Today, several scientists recommend shielding the video display terminals for such radiation. Among others, this includes Dr. H. D. Sharma, University of Waterloo, Toronto, Canada and Dr. Art Guy, Professor at University of Washington, Seattle, Wash., in a report to International Business Machine Corporation.
There is also a problem created by use of video display terminals in lighted areas where glare from the reflection of the surrounding lighting causes the user of the video display terminal to complain.